Cooperative Diversity in Wireless Networks with Stochastic and Bursty Traffic

This work investigates the asymptotic error performance of outage-limited communications in cooperative wireless relay networks, with fading that is quasi-static, with an information-arrival process that is stochastic and bursty, and with bits that have a strictly limited lifespan. Employing large- deviation techniques, we analyze the probability of bit error where such errors are due to both erroneous decoding as well as due to delay violation. We derive a tradeoff between, on one hand, the optimal negative SNR exponent of the total probability of error, and on the other hand, the ratio of the average bit- arrival rate to the ergodic capacity of the channel. This is for the case of the orthogonal amplify-and-forward protocol, constant system loading, many flows and asymptotically high values of SNR. The tradeoff holds for any delay limitation. As a practical consequence, the tradeoff tells us how to better balance the effects of channel atypicality (outage) and burstiness atypicality, by proper choice of transmission rate and by optimizing the cooperative cluster size, i.e., limiting the cooperation to a specific subset of the cooperative users.